Newly Described Copepod Apocyclops cmfri sp. nov. as a Potential Replacement for Artemia nauplii in the Larval Rearing of Vermiculated Spinefoot Rabbitfish (Siganus vermiculatus)

Abstract

This study evaluated the suitability of a new copepod, Apocyclops cmfri, as a live feed for larval rearing of Siganus vermiculatus. Total length (TL) and mouth opening (MO) of rabbitfish larvae increased exponentially with age (initial TL = 2.04 ± 0.096 mm; growth rate = 0.0657 day⁻¹ ± 0.00166; t-values for a and b = 21.13 and 39.69; p  < 0.001). Segmented regression analysis of MO–TL relationship identified a significant breakpoint at TL ≈ 8.96 mm (95% confidence interval), indicating a threshold for ingestion of A. cmfri adults and the gut content analysis confirmed the same. Feeding experiments from 22 day post hatch (dph), with larvae fed either Artemia nauplii alone at 5 or 1 individuals mL⁻¹ or a combination of A. cmfri (4 individuals mL⁻¹) and Artemia nauplii (1 individuals mL⁻¹) revealed that at 50 dph, larvae fed Artemia nauplii alone at 5 individuals mL⁻¹ achieved a length gain of 232.24% (survival 43.33%; metamorphosis rate 46.67%), which was not significantly different (p  > 0.05) from that fed the combination of A. cmfri adults and Artemia nauplii (222.37% length gain, 40.0% survival; 43.66% metamorphosis rate). Essential amino acids constituted 59.58% and 50.58% of the total amino acids in A. cmfri adults and unenriched Artemia nauplii respectively. In A. cmfri adults, EPA and DHA were 2.1 and 3.8% (in 1:1.81 ratio) whereas in unenriched Artemia nauplii, the content was minimal. These findings support the use of A. cmfri as a viable partial replacement to Artemia nauplii for sustainable marine hatchery practices.